Method and means for operating a soaking pit



1962 A. A. FENNELL 3,051,462

METHOD AND MEANS FOR OPERATING A SOAKING PIT Filed March 12, 1959 2Sheets-Sheet 1 PORTR MRO cnsO

umin' Aug. 28, 1962 A. A. FENNELL 3,051,462

METHOD AND MEANS FOR OPERATING A SOAKING PIT 2 Sheets-Sheet 2 FiledMarch 12, 1959 9n. R w W W m H i E d M m w/ m M m 5 M 0 m a WNssss QM mm x i l mm 81%. Q NN Q WWIULIS UI I 1 3% U II V U HU wwn- IIDH A W U NMQ3,051,462 METHOD AND MEANS FOR OPERATING A SOAKING PIT Anthony A.Fennell, Homewood, Ill. 379 E. 147th St., Harvey, 111.) Filed Mar. 12,1959, Ser. No. 799,030 7 Claims. (Cl. 263-15) This invention relatesgenerally to furnaces for heating ingots and more particularly to animproved method of operating a regenerative-type furnace which may beemployed in heating ingots.

Brick-lined, pit-type furnaces are frequently used for heating ingots inorder to prepare the ingots fo-r subsequent rolling or forging.Commonly, the heating efliciency of such soaking pits is increased bythe provision of checker chambers, brickwork heat exchangers built withalternate open spaces. Furnaces, so provided are called regenerative.

According to conventional practice, two checker chambers are employed sothat incomping air may be heated as it passes over the brickwork in onechamber while exhaust gases passing out of the soaking pit heat thebrickwork in the other chamber. The flow of air and exhaust gases areperiodically reversed. Fuel, naturally, is introduced only at theburners associated with incoming air.

Heretofore, reversing of the flow of air and exhaust gases has beencontrolled according to the temperature differential existing betweenthe two checker chambers, or according to a uniform, fixed, timeinterval. By either method, rather slow heating rates must be used inorder to prevent overheating and burning of the ingots since the flamesactually impinge the ingots and high flame temperatures are encouragedby preheating the incoming air in the checker chamber.

Especially with regard to steels, overheating results in an enlargedgrain size and impaired physical properties. Burning is an extremelyoverheated condition which allows the fusible constituents to melt andrun into the grain bounderies leaving voids between the grains.

Even when rather slow heating rates are used in conventional,regenerative-type soaking pits, some overheating and burning has beenknown to occur, particularly with regard to sensitive metals and alloys.

Therefore, a general object of the present invention is to provide animproved method of operating a regenerative-type soaking pit.

States Patent Another object of the invention is to provide a methodof'operating a regenerative-type soaking pit, which method involvesfiring a plurality of burners in sequence according to the error betweenthe actual temperature in the pit and the required temperature.

Yet another object of the invention is to provide an improved system forheating ingots which obviates overheating to a hitherto unknown degree.

A further object of the invention is to provide an improved system forheating ingots which is permissive of rapid heating rates.

A still further object of the invention is to provide a novel firingsequencer for regenerative-type soaking pits.

Additional objects and features of the invention pertain to theparticular structure and arrangements whereby the above objects areattained.

The invention, both to its structure and mode of operation, will bebetter understood by reference to the following disclosure and drawingsforming a part thereof,

FIG. 3 is a view of a control box incorporating parts of the firingsequencer of FIG. 2.

A system for heating ingots constructed in accordance with a preferredembodiment of the invention includes a brick-lined, pit-type furnace orsoaking pit 10 provided with four ports, port A, port B, port C and portD. It is recognized, however, that a number of ports other than four maybe readily utilized.

Port A communicates with a checker chamber or heat exchanger 12a bymeans of a passageway 14a. Checker chamber 12a terminates at one end ina flue 16a which includes a draft reversing valve 18a. Air from ablower, not shown, may be introduced between the top of the chamber 12aand the reversing valve 18a through a manifold 20a. Advantageously,manifold 20a is provided with a draft control gate 22a.

For purposes of injecting ignited fuel into the incoming air streamentering through port A, there is provided a burner 24a juxtaposed withthe port A. Burner 24a is appropriately connected to a fuel valvearrangement 26a which is adapted to supply suitable fuel ingredients. Asis well known, oil, natural gas, and manufactured gas have proved to beappropriate fuels. In effect, the burner 24a transduces the potentialsource energy of the fuel to actual heat energy in the furnace.

In one useful embodiment, fuel valve arrangement 26a is comprised of anair-operated fuel valve 28a. Appropriately, a solenoid valve 30a worksfuel valve 28a through a diaphragm air motor 32a mounted on valve 28a.

Like elements associated with the ports B, C and D have been denoted bylike numerals to which have been added the appropriate suflix letter.

In order to coordinate the several operating elements, there is provideda firing sequencer 34- which includes a control unit 36, a temperaturemeasuring element 38 mounted in the wall of furnace 110 and atemperature controller 40 connected between control unit 36 andmeasuring element 38. So that the instantaneous condition under whichfurnace 10 is operating may be perceived at a glance, control unit 36has a number of indicator lights 42 mounted to its face. As shown, theseveral lights 42 may be adapted to provide an indication of thecondition ,of the materials being supplied to the various ports infurnace 10.

With reference to FIG. 3, the control unit 36 may be composed of ahousing or enclosure 44 to which a door 46 is swingably mounted. In theinstance wherein lights 42 are transformer-type lights, correspondingtransformers 48 are afiixed to the back of door 46 to be connectedappropriately with the lights 42. The transformers 48 are supplied withpower from a suitable source by means of the connector block 50.

Other important elements of the firing sequencer 34 are contained withinthe housing 44. Among these elements is a shunt-wound DC. motor 52 whichis adapted to rotate a camshaft 54 through a speed reducer or gear train56 interconnected therebetween. Three groups of timing elements takingthe form of segmented cams, cams 58, cams 60, and earns 62, are mountedon the camshaft 54 in order to operate respectively switches 64,switches 66 and switches 68. Switches 68 are adapted to operate a purgetimer 70.

Enclosure 44 may also house purge relays 72 and a sequencing relay 74.Electrical power may be supplied to the motor 52, the switches 64, theswitches 66 and the switches 68 by means of the connector block 76.

As indicated in FIG. 2, the speed at which the camshaft 54 is rotated bymotor 52 is governed through temperature controller 40. In response tothe output of the measuring element 38, temperature controller 40operates a rheostat 78 which is connected in series with a DC. source 80and the shunt field of motor 52. Thus, as the temperature within furnace=10 increases, temperature controller 40 moves to reduce the fieldresistance included by means of rheostat 78; and accordingly, motor 52may be made to operate at a gradually increasing speed.

As is also shown in FIG. 2, the switches 66 operate damper reversingsolenoids 82 whereas switches 64 operate pressure switches 84. Switches84 are conditioned by the solenoids 82. As is also indicated in FIG. 2,the purge relays 72 are conditioned by the sequencing relay 74, relay 74responding to the output of the purge timer 7 which is operated byswitches 68. The output of purge relays 72 is directed to the valves 30which are operated thereby. Specifically, a switch 64, a switch 84 and apurge relay 72 are electrically connected in series with each of thevalves 30. When a switch 64 is closed by the cooperating cam 58, thecorresponding switch 84 must also be closed before current will bepassed to the corresponding purge relay 72. The purge relay 72 must beconditioned, i.e. its contacts must be closed as by the operation ofsequencing relay 74, before any current passed by the switches 64 and 84can be passed, in turn, to the valve 30. The switches 64 may be groupedwith the switches 84 to form what may be termed a conditioning means.Similarly, the solenoids 82 and the switches 66 may be grouped to formwhat may be termed a conditioning means. Furthermore, the relays 72, theswitches 68, purge timer 70 and sequencing relay 74 may also be groupedfor convenience defining what may be termed an operating means for thevalves 30.

For purposes of providing an easy understanding of the invention, it isadvantageous to provide at this juncture a functional description of themode of operation of the component parts, given with reference to TableI which traces a firing sequence for the embodiment shown in thefigures.

Table I Cycle Stage Port(s) Port(s) Ex- Open Valves Closed Valves Firinghausting O and D 28a, I); 180, d 280, d; 1811, b. D and A 28!); 18d, a28a, c,d;l b,c. D and A 281), 0; 1811, d 280, d;18b, c. A and B 281:;18b d; l c, d. A and B 280, d; 1811, 180, d. B and 0-. 28d; 18!), c c;18d,a. B and 0-. 28d, a: 18b, c 18 d. 4purge O and D 28a; 180, d 811, b.Damper 18a.

Assuming that furnace 10 has been charged with ingots, and that thesystem is prepared for operation, power may be applied to the firingsequencer 34 in order to initiate heating.

Having the cams 58, 60 and 62 positioned so that stage 1 of the firingsequence will be realized, burners 24a and 24b will have fuel directedtherethrough by means of the fuel valves 28a and 28b which have beenactuated by the solenoid valves a and 30b respectively. Valves 30a and30b act thus in response to the signals from the switches 64, which areclosed by the appropriate segmented earns 58. These signals are passedappropriately by the pressure switches 84 and the purge relays 72.

In stage 1, air is directed through the chambers 12a and 12b from themanifolds 20a and 20b respectively, draft reversing valves 18a and 18bbeing closed. Furthermore, exhaust gases pass through ports C and D; andvalves 18c and 18d are therefore open. The valves 28c and 28d are closedin order to prevent firing the burners 24c and 24d.

The next successive stage in the firing sequence is denoted l-purge inTable I. This condition is achieved by motor 52 appropriately rotatingcam shaft 54 and thereby altering the condition of the switches 64, 66and 68. Accordingly, valve 28b is left open in continuation of thefiring of burner 24b. Valve 180 is closed in order to clear the exhaustgases from the chamber 12c and the passageway 14c prior to thesubsequent firing of burner 24c. Appropriately, valve 280 remainsclosed.

Valve 18a and valve 28a are closed during the 1- purge stage since portA is being changed over from firing to exhausting. Valves 18d and 28dremain in their former condition as port D continues in the exhaustingcondition.

In similar manner the firing sequence progresses from one cycle stage tothe next, stage 1 following stage 4 in continuation of the heat. Whenfurnace 10 eventually reaches the temperature set on controller 40, thedamper condition is achieved. At this stage, the entire furnace isclosed down in order to allow the ingots which have been charged thereinto absorb heat from the furnace walls and to equalize in temperature.This damper stage continues until the charged ingots have absorbedsufficient heat to depress the furnace temperature, as sensed by thetemperature measuring element 38, thereby to initiate a new firingsequence.

It should be noted that FIG. 1 specifically illustrates cycle stage 3.It is also important to point out that the draft control gates 22 areordinarily not varied in position during the firing sequence.

Having one firing sequence thus described, it is apparent that thisfiring sequence will be repeated in gradually increasing tempo as thetemperature of the furnace and the ingots charged therein increases andas the temperature controller 40 gradually reduces the resistance in thefield of motor 52 by means of the rheostat 78. For example, the firstfiring sequence might extend over a five minute interval, and the lastfiring sequence before the damper stage is achieved might extend overonly a oneand-one-half minute interval. Thus, overheating of the ingotsis obviated for, while the flames still impinge the ingots, they do sofor very short periods and, as the danger of overheating increases withthe increasing temperature of the ingots, the flames impinge for evershortening periods.

The specific example herein shown and described is illustrative only.Various changes in structure and method of operation will, no doubt,occur to those skilled in the art; and these changes are to beunderstood as forming a part of this invent-ion insofar as they fallwithin the spirit and scope of the appended claims.

The invention is claimed as follows:

1. A system for heating materials comprising: a furnace; a plurality ofenergy transducers arranged to deliver heat energy to the interior ofsaid furnace; regulating means for each of said transducers controllablysupplying source energy thereto; rotatable shaft means external to saidfurnace; means for periodically and unidirectionally rotating said shaftmeans at a speed proportional to the temperature within said furnace;means individually conditioning said regulating means for operation; afirst plurality of timing means on said shaft means individ-, uallyactuating said conditioning means in sequence; means individuallyoperating said regulating means when said regulating means have beenreadied for operation by said conditioning means; and a second pluralityof timing means on said shaft means individually actuating saidoperating means in sequence, whereby to supply source energy to saidtransducers periodically and at selected intervals and whereby to varysaid intervals according to the temperature within said furnace in orderto minimize overheating of materials introduced therein.

2. A system for heating materials comprising: a furnace; aplurality ofenergy transducers arranged to deliver heat energy to the interior ofsaid furnace; regulating means for each of said transducers controllablysupplying source energy thereto; rotatable shaft means external to saidfurnace; means for periodically and unidirectionally rotating said shaftmeans at a speed directly proportional to the temperature within saidfurnace, including temperature responsive means for sensing saidtemperature and for providing an output indicative thereof and furtherincluding drive means operated in accordance with said output; meansindividually conditioning said regulating means for operation; a firstplurality of timing means on said shaft means individually actuatingsaid conditioning means in sequence; means individually operating saidregulating means when said regulating means have been readied foroperation by said conditioning means; and a second plurality of timingmeans on said shaft means individually actuating said operating means insequence, whereby to supply source energy to said transducersperiodically and at selected intervals and whereby to vary saidintervals according to the temperature within said furnace in order tominimize overheating of materials introduced therein.

3. A system for heating materials comprising: a furnace structure havinga plurality of ports communicating exteriorly thereto; a plurality ofheat exchangers connected individually to said ports and reversiblyassociated with inlet oxidizing gases and outlet exhaust gases; draftreversing means arranged with each of said heat exchangers; a pluralityof energy transducers arranged to deliver heat energy to the interior ofsaid furnace, said transducers being individually arranged with saidports; regulating means for each of said transducers controllablysupplying source energy thereto; rotatable shaft means external to saidfurnace; means for periodically and unidirectionally rotating said shaftmeans at a speed proportional to the temperature within said furnace;first means individually conditioning said regulating means foroperation; a first plurality of timing means on said shaft meansindividually actuating said conditioning means in sequence; second meansindividually conditioning said regulating means for operation andsimultaneously operating said draft reversing means; a second pluralityof timing means on said shaft means individually actuating said secondconditioning means in sequence; means individually operating saidregulating means when said regulating means have been readied foroperation by said first and second conditioning means; and a thirdplurality of timing means on said shaft means individually actuatingsaid operating means in sequence, whereby to supply source of energy tosaid transducers periodically and at selected intervals and whereby tovary said intervals according to the temperature within said furnace inorder to minimize overheating of materials introduced therein.

4. A system for heating materials comprising: a furnace structure havinga plurality of ports communicating exteriorly thereto; a plurality ofheat exchangers connected individually to said ports and reversiblyassociated with inlet oxidizing gases and outlet exhaust gases; draftreversing means arranged with each of said heat exchangers; a pluralityof energy transducers arranged to deliver heat energy to the interior ofsaid furnace, each of said transducers being arranged with one of saidports; regulating means for each of said transducers controllablysupplying source energy thereto and including a solenoidoperated valve;rotatable shaft means external to said furnace; means for periodicallyand unidirectionally rotating said shaft means at a speed directlyproportional to the temperature within said furnace, includingtemperature responsive means for sensing said temperature and forproviding an output indicative thereof and further including drive meansoperated in accordance with said output; first means individuallyconditioning said regulating means for operation including a firstplurality of electrical switches; a first plurality of timing cams onsaid shaft means individually actuating said first conditioning means insequence; second means individually conditioning said regulating meansfor operation and simultaneously operating said draft reversing means,including a plurality of damper reversing solenoids and a. secondplurality of electrical switches; a second plurality of timing cams onsaid shaft means individually actuating said second conditioning meansin sequence; means individually operating said regulating means whensaid regulating means have been readied for operation by said first andsecond conditioning means, including a third plurality of electricalswitches connected to said solenoidoperated valves through a pluralityof relays individually controlled by said first plurality of electricalswitches; and a third plurality of timing cams on said shaft meansindividually actuating said operating means in sequence, whereby tosupply source energy to said transducers periodically and at selectedintervals and whereby to vary said intervals according to thetemperature within said furnace in order to minimize overheating ofmaterials introduced therein.

5. The method of heating a soaking pit to a desired temperature by aplurality of burners, which method is characterized by the steps of:firing the plurality of burners in a predetermined repeated order toestablish a heating cycle over a starting period of time; sensing thetemperature within said pit; and reducing the period of time required tocomplete the repeated order of firing in the heating cycle in accordancewith the approach of temperature sensed within the pit to said desiredtemperature.

6. A firing sequencer for a regenerative-type soaking pits comprising: ahousing; a plurality of fuel control valves spaced apart from saidhousing; means for operating said valves; a camshaft rotatably mountedin said housing; drive means for said camshaft; means for increasing theoutput shaft speed of said drive means as the temperature of said pit isincreased; including means sensing the temperature of said pit and meansoperatively connected to said sensing means for varying the input tosaid drive means in accordance with changes in said temperature; and aplurality of cams affixed to said camshaft and arranged to operate saidvalve operating means in sequence.

7. A firing sequencer in combination with a regenerative-type soakingpit and comprising: a housing; a plurality of fuel control valves spacedapart from said housing; a plurality of purge relays arranged withinsaid housing; a plurality of pressure switches individually connected inseries with said purge relays; a camshaft rotatably mounted in saidhousing; drive means for said camshaft; means for increasing the outputshaft speed of said drive means as the temperature of said pit isincreased and including means sensing the temperature of said pit andmeans operatively connected to said sensing means for varying the inputto said drive means in accordance with changes in said temperature; afirst plurality of cams affixed to said camshaft and arranged to operatesequentially said fuel control valves through said pressure switches andthrough said purge relays, the period over which said sequentialoperation occurs being reduced in proportion to the reduction intemperature error of said pit; a plurality of damper reversing solenoidsadapted to condition said pressure switches; a second plurality of camsaffixed to said camshaft and arranged to operate sequentially saiddamper reversing solenoids; a sequencing relay adapted to condition saidpurge relays; a purge timer connected in series with said sequencingrelay; and a third plurality of cams affixed to said camshaft andarranged to operate said purge timer, whereby to minimize overheating ofmaterials introduced into said pit.

References Cited in the file of this patent UNITED STATES PATENTS2,095,906 Beck Oct. 12, 1937 2,163,510 Cantrell et al. June 20, 19392,429,880 Hays Oct. 28, 1947

